Re: [PATCH v3] f2fs: submit cached bio to avoid endless PageWriteback

[Chao Yu <yuchao0@huawei.com>]

On 2018/9/26 9:42, Jaegeuk Kim wrote:
> On 09/26, Chao Yu wrote:
>> On 2018/9/26 8:20, Jaegeuk Kim wrote:
>>> On 09/21, Chao Yu wrote:
>>>> On 2018/9/18 10:14, Chao Yu wrote:
>>>>> On 2018/9/18 10:02, Jaegeuk Kim wrote:
>>>>>> On 09/18, Chao Yu wrote:
>>>>>>> On 2018/9/18 9:37, Jaegeuk Kim wrote:
>>>>>>>> On 09/18, Chao Yu wrote:
>>>>>>>>> On 2018/9/18 9:04, Jaegeuk Kim wrote:
>>>>>>>>>> On 09/13, Chao Yu wrote:
>>>>>>>>>>> From: Chao Yu <yuchao0@huawei.com>
>>>>>>>>>>>
>>>>>>>>>>> When migrating encrypted block from background GC thread, we only add
>>>>>>>>>>> them into f2fs inner bio cache, but forget to submit the cached bio, it
>>>>>>>>>>> may cause potential deadlock when we are waiting page writebacked, fix
>>>>>>>>>>> it.
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>>>>>>>> ---
>>>>>>>>>>> v3:
>>>>>>>>>>> clean up codes suggested by Jaegeuk.
>>>>>>>>>>>  fs/f2fs/f2fs.h |  2 +-
>>>>>>>>>>>  fs/f2fs/gc.c   | 71 +++++++++++++++++++++++++++++++++++---------------
>>>>>>>>>>>  fs/f2fs/node.c | 13 ++++++---
>>>>>>>>>>>  3 files changed, 61 insertions(+), 25 deletions(-)
>>>>>>>>>>>
>>>>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>>>>>> index b676b82312e0..917b2ca76aac 100644
>>>>>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>>>>>> @@ -2869,7 +2869,7 @@ struct page *f2fs_new_node_page(struct dnode_of_data *dn, unsigned int ofs);
>>>>>>>>>>>  void f2fs_ra_node_page(struct f2fs_sb_info *sbi, nid_t nid);
>>>>>>>>>>>  struct page *f2fs_get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid);
>>>>>>>>>>>  struct page *f2fs_get_node_page_ra(struct page *parent, int start);
>>>>>>>>>>> -void f2fs_move_node_page(struct page *node_page, int gc_type);
>>>>>>>>>>> +int f2fs_move_node_page(struct page *node_page, int gc_type);
>>>>>>>>>>>  int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>>>>>>>>>>>  			struct writeback_control *wbc, bool atomic,
>>>>>>>>>>>  			unsigned int *seq_id);
>>>>>>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>>>>>>>> index a4c1a419611d..f57622cfe058 100644
>>>>>>>>>>> --- a/fs/f2fs/gc.c
>>>>>>>>>>> +++ b/fs/f2fs/gc.c
>>>>>>>>>>> @@ -461,7 +461,7 @@ static int check_valid_map(struct f2fs_sb_info *sbi,
>>>>>>>>>>>   * On validity, copy that node with cold status, otherwise (invalid node)
>>>>>>>>>>>   * ignore that.
>>>>>>>>>>>   */
>>>>>>>>>>> -static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>>> +static int gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  		struct f2fs_summary *sum, unsigned int segno, int gc_type)
>>>>>>>>>>>  {
>>>>>>>>>>>  	struct f2fs_summary *entry;
>>>>>>>>>>> @@ -469,6 +469,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  	int off;
>>>>>>>>>>>  	int phase = 0;
>>>>>>>>>>>  	bool fggc = (gc_type == FG_GC);
>>>>>>>>>>> +	int submitted = 0;
>>>>>>>>>>>  
>>>>>>>>>>>  	start_addr = START_BLOCK(sbi, segno);
>>>>>>>>>>>  
>>>>>>>>>>> @@ -482,10 +483,11 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  		nid_t nid = le32_to_cpu(entry->nid);
>>>>>>>>>>>  		struct page *node_page;
>>>>>>>>>>>  		struct node_info ni;
>>>>>>>>>>> +		int err;
>>>>>>>>>>>  
>>>>>>>>>>>  		/* stop BG_GC if there is not enough free sections. */
>>>>>>>>>>>  		if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0))
>>>>>>>>>>> -			return;
>>>>>>>>>>> +			return submitted;
>>>>>>>>>>>  
>>>>>>>>>>>  		if (check_valid_map(sbi, segno, off) == 0)
>>>>>>>>>>>  			continue;
>>>>>>>>>>> @@ -522,7 +524,9 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  			continue;
>>>>>>>>>>>  		}
>>>>>>>>>>>  
>>>>>>>>>>> -		f2fs_move_node_page(node_page, gc_type);
>>>>>>>>>>> +		err = f2fs_move_node_page(node_page, gc_type);
>>>>>>>>>>> +		if (!err && gc_type == FG_GC)
>>>>>>>>>>> +			submitted++;
>>>>>>>>>>>  		stat_inc_node_blk_count(sbi, 1, gc_type);
>>>>>>>>>>>  	}
>>>>>>>>>>>  
>>>>>>>>>>> @@ -531,6 +535,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  
>>>>>>>>>>>  	if (fggc)
>>>>>>>>>>>  		atomic_dec(&sbi->wb_sync_req[NODE]);
>>>>>>>>>>> +	return submitted;
>>>>>>>>>>>  }
>>>>>>>>>>>  
>>>>>>>>>>>  /*
>>>>>>>>>>> @@ -666,7 +671,7 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>>>>>>>>>>>   * Move data block via META_MAPPING while keeping locked data page.
>>>>>>>>>>>   * This can be used to move blocks, aka LBAs, directly on disk.
>>>>>>>>>>>   */
>>>>>>>>>>> -static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>>> +static int move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>>>  				int gc_type, unsigned int segno, int off)
>>>>>>>>>>
>>>>>>>>>> We don't need to submit IOs in this case.
>>>>>>>>>
>>>>>>>>> Actually, previously, we missed to submit IOs for encrypted block only in
>>>>>>>>> BGGC, so we fix to submit for this case, all other codes are cleanups. Right?
>>>>>>>>
>>>>>>>> The move_data_block migrates encrypted blocks all the time with meta page IOs.
>>>>>>>> I don't know what you're saying about BGGC.
>>>>>>>
>>>>>>> In move_data_block(), we use f2fs_submit_page_write() to add encrypted page
>>>>>>> in to sbi->write_io[META].bio cache, so before exit GC, we need to submit
>>>>>>> this cache by f2fs_submit_merged_write(), otherwise bio with encrypted page
>>>>>>> will be cached in sbi->write_io[META].bio for long time, since we only
>>>>>>> submmit this bio cache in foreground GC.
>>>>>>>
>>>>>>> if (gc_type == FG_GC)
>>>>>>> 	f2fs_submit_merged_write(sbi,
>>>>>>> 				(type == SUM_TYPE_NODE) ? NODE : DATA);
>>>>>>
>>>>>> Does this issue pending META IOs? I think META won't block any NODE/DATA
>>>>>> pages. Moreover checkpoint or reading the moved block make the IOs be flushed,
>>>>>> so it doesn't hurt the consistency.
>>>>
>>>> It may cause long latency before someone flushes the meta IO, how about flushing
>>>> IO like other flows, like writepages?
>>>>
>>>> Or is there any benefit that we still cache meta IO after GC?
>>>>
>>>>>
>>>>> I just guess below endless waiting for page writeback is cased by this case
>>>>
>>>> Any thoughts?
>>>
>>> I'm waiting for the previous reported issue. Do we have this in products?
>>
>> I didn't see such stack in products.
>>
>> BTW, I added one patch in my tree, although this patch is not correct now
>> since it is missing to submit bio in some cases, it can easily reproduce
>> such stack, so I guess there is still at least one place we didn't submit
>> bio correctly.
> 
> How can we easily reproduce this? Why do we need to submit all of them?

In f2fs_write_cache_pages(), if we only check page with last_idx is not enough?

1. cache page (idx = 1) in cold data bio cache
2. cache page (idx = 2) in warm data bio cache and submitted bio cache
3. f2fs_submit_merged_write_cond tries to check page (idx = 2), but this
page is not in bio cache, so we missed to submit code data bio cache, right?

Thanks,

> 
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git/commit/?h=f2fs-dev&id=2ca666658fc1958ab176030d435efa2ce325aa52
>>
>> Thanks,
>>
>>>
>>>>
>>>>>
>>>>> -000|__switch_to()
>>>>>
>>>>> -001|__schedule()
>>>>>
>>>>> -002|need_resched(inline)
>>>>>
>>>>> -002|schedule()
>>>>>
>>>>> -003|schedule_timeout()
>>>>>
>>>>> -004|get_current(inline)
>>>>>
>>>>> -004|io_schedule_timeout()
>>>>>
>>>>> -005|bit_wait_io()
>>>>>
>>>>> -006|__wait_on_bit()
>>>>>
>>>>> -007|wait_on_page_bit()
>>>>>
>>>>> -008|PageWriteback(inline)
>>>>>
>>>>> -008|wait_on_page_writeback(inline)
>>>>>
>>>>> -008|__filemap_fdatawait_range()
>>>>>
>>>>> -009|filemap_fdatawait_keep_errors()
>>>>>
>>>>> -010|sync_inodes_sb()
>>>>>
>>>>> -011|__sync_filesystem(inline)
>>>>>
>>>>> -011|sync_filesystem()
>>>>>
>>>>> -012|generic_shutdown_super()
>>>>>
>>>>> -013|kill_block_super()
>>>>>
>>>>> -014|kill_f2fs_super()
>>>>>
>>>>> -015|deactivate_locked_super()
>>>>>
>>>>> -016|deactivate_super()
>>>>>
>>>>> -017|mnt_free_id(inline)
>>>>>
>>>>> -017|cleanup_mnt()
>>>>>
>>>>> -018|__cleanup_mnt()
>>>>>
>>>>> -019|task_work_run()
>>>>>
>>>>> -020|do_notify_resume()
>>>>>
>>>>> -021|work_pending(asm)
>>>>>
>>>>> -->|exception
>>>>>
>>>>> -022|NUX:0x539E58(asm)
>>>>>
>>>>> ---|end of frame
>>>>>
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>>  {
>>>>>>>>>>>  	struct f2fs_io_info fio = {
>>>>>>>>>>> @@ -685,25 +690,29 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>>>  	struct node_info ni;
>>>>>>>>>>>  	struct page *page, *mpage;
>>>>>>>>>>>  	block_t newaddr;
>>>>>>>>>>> -	int err;
>>>>>>>>>>> +	int err = 0;
>>>>>>>>>>>  	bool lfs_mode = test_opt(fio.sbi, LFS);
>>>>>>>>>>>  
>>>>>>>>>>>  	/* do not read out */
>>>>>>>>>>>  	page = f2fs_grab_cache_page(inode->i_mapping, bidx, false);
>>>>>>>>>>>  	if (!page)
>>>>>>>>>>> -		return;
>>>>>>>>>>> +		return -ENOMEM;
>>>>>>>>>>>  
>>>>>>>>>>> -	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>>>>>>>>> +	if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
>>>>>>>>>>> +		err = -ENOENT;
>>>>>>>>>>>  		goto out;
>>>>>>>>>>> +	}
>>>>>>>>>>>  
>>>>>>>>>>>  	if (f2fs_is_atomic_file(inode)) {
>>>>>>>>>>>  		F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>>>>>>>>>>>  		F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>>>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>>>  		goto out;
>>>>>>>>>>>  	}
>>>>>>>>>>>  
>>>>>>>>>>>  	if (f2fs_is_pinned_file(inode)) {
>>>>>>>>>>>  		f2fs_pin_file_control(inode, true);
>>>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>>>  		goto out;
>>>>>>>>>>>  	}
>>>>>>>>>>>  
>>>>>>>>>>> @@ -714,6 +723,7 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>>>  
>>>>>>>>>>>  	if (unlikely(dn.data_blkaddr == NULL_ADDR)) {
>>>>>>>>>>>  		ClearPageUptodate(page);
>>>>>>>>>>> +		err = -ENOENT;
>>>>>>>>>>>  		goto put_out;
>>>>>>>>>>>  	}
>>>>>>>>>>>  
>>>>>>>>>>> @@ -796,6 +806,7 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>>>  	fio.new_blkaddr = newaddr;
>>>>>>>>>>>  	f2fs_submit_page_write(&fio);
>>>>>>>>>>>  	if (fio.retry) {
>>>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>>>  		if (PageWriteback(fio.encrypted_page))
>>>>>>>>>>>  			end_page_writeback(fio.encrypted_page);
>>>>>>>>>>>  		goto put_page_out;
>>>>>>>>>>> @@ -819,34 +830,42 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>>>>>>  	f2fs_put_dnode(&dn);
>>>>>>>>>>>  out:
>>>>>>>>>>>  	f2fs_put_page(page, 1);
>>>>>>>>>>> +	return err;
>>>>>>>>>>>  }
>>>>>>>>>>>  
>>>>>>>>>>> -static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>>> +static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>>>  							unsigned int segno, int off)
>>>>>>>>>>>  {
>>>>>>>>>>>  	struct page *page;
>>>>>>>>>>> +	int err = 0;
>>>>>>>>>>>  
>>>>>>>>>>>  	page = f2fs_get_lock_data_page(inode, bidx, true);
>>>>>>>>>>>  	if (IS_ERR(page))
>>>>>>>>>>> -		return;
>>>>>>>>>>> +		return PTR_ERR(page);
>>>>>>>>>>>  
>>>>>>>>>>> -	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>>>>>>>>> +	if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
>>>>>>>>>>> +		err = -ENOENT;
>>>>>>>>>>>  		goto out;
>>>>>>>>>>> +	}
>>>>>>>>>>>  
>>>>>>>>>>>  	if (f2fs_is_atomic_file(inode)) {
>>>>>>>>>>>  		F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>>>>>>>>>>>  		F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>>>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>>>  		goto out;
>>>>>>>>>>>  	}
>>>>>>>>>>>  	if (f2fs_is_pinned_file(inode)) {
>>>>>>>>>>>  		if (gc_type == FG_GC)
>>>>>>>>>>>  			f2fs_pin_file_control(inode, true);
>>>>>>>>>>> +		err = -EAGAIN;
>>>>>>>>>>>  		goto out;
>>>>>>>>>>>  	}
>>>>>>>>>>>  
>>>>>>>>>>>  	if (gc_type == BG_GC) {
>>>>>>>>>>> -		if (PageWriteback(page))
>>>>>>>>>>> +		if (PageWriteback(page)) {
>>>>>>>>>>> +			err = -EAGAIN;
>>>>>>>>>>>  			goto out;
>>>>>>>>>>> +		}
>>>>>>>>>>>  		set_page_dirty(page);
>>>>>>>>>>>  		set_cold_data(page);
>>>>>>>>>>>  	} else {
>>>>>>>>>>> @@ -864,7 +883,6 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>>>  			.io_type = FS_GC_DATA_IO,
>>>>>>>>>>>  		};
>>>>>>>>>>>  		bool is_dirty = PageDirty(page);
>>>>>>>>>>> -		int err;
>>>>>>>>>>>  
>>>>>>>>>>>  retry:
>>>>>>>>>>>  		set_page_dirty(page);
>>>>>>>>>>> @@ -889,6 +907,7 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>>>  	}
>>>>>>>>>>>  out:
>>>>>>>>>>>  	f2fs_put_page(page, 1);
>>>>>>>>>>> +	return err;
>>>>>>>>>>>  }
>>>>>>>>>>>  
>>>>>>>>>>>  /*
>>>>>>>>>>> @@ -898,7 +917,7 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>>>>>>>   * If the parent node is not valid or the data block address is different,
>>>>>>>>>>>   * the victim data block is ignored.
>>>>>>>>>>>   */
>>>>>>>>>>> -static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>>> +static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>>>  		struct gc_inode_list *gc_list, unsigned int segno, int gc_type)
>>>>>>>>>>>  {
>>>>>>>>>>>  	struct super_block *sb = sbi->sb;
>>>>>>>>>>> @@ -906,6 +925,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>>>  	block_t start_addr;
>>>>>>>>>>>  	int off;
>>>>>>>>>>>  	int phase = 0;
>>>>>>>>>>> +	int submitted = 0;
>>>>>>>>>>>  
>>>>>>>>>>>  	start_addr = START_BLOCK(sbi, segno);
>>>>>>>>>>>  
>>>>>>>>>>> @@ -922,7 +942,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>>>  
>>>>>>>>>>>  		/* stop BG_GC if there is not enough free sections. */
>>>>>>>>>>>  		if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0))
>>>>>>>>>>> -			return;
>>>>>>>>>>> +			return submitted;
>>>>>>>>>>>  
>>>>>>>>>>>  		if (check_valid_map(sbi, segno, off) == 0)
>>>>>>>>>>>  			continue;
>>>>>>>>>>> @@ -994,6 +1014,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>>>  		if (inode) {
>>>>>>>>>>>  			struct f2fs_inode_info *fi = F2FS_I(inode);
>>>>>>>>>>>  			bool locked = false;
>>>>>>>>>>> +			int err;
>>>>>>>>>>>  
>>>>>>>>>>>  			if (S_ISREG(inode->i_mode)) {
>>>>>>>>>>>  				if (!down_write_trylock(&fi->i_gc_rwsem[READ]))
>>>>>>>>>>> @@ -1013,12 +1034,16 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>>>  			start_bidx = f2fs_start_bidx_of_node(nofs, inode)
>>>>>>>>>>>  								+ ofs_in_node;
>>>>>>>>>>>  			if (f2fs_post_read_required(inode))
>>>>>>>>>>> -				move_data_block(inode, start_bidx, gc_type,
>>>>>>>>>>> -								segno, off);
>>>>>>>>>>> +				err = move_data_block(inode, start_bidx,
>>>>>>>>>>> +							gc_type, segno, off);
>>>>>>>>>>>  			else
>>>>>>>>>>> -				move_data_page(inode, start_bidx, gc_type,
>>>>>>>>>>> +				err = move_data_page(inode, start_bidx, gc_type,
>>>>>>>>>>>  								segno, off);
>>>>>>>>>>>  
>>>>>>>>>>> +			if (!err && (gc_type == FG_GC ||
>>>>>>>>>>> +					f2fs_post_read_required(inode)))
>>>>>>>>>>> +				submitted++;
>>>>>>>>>>> +
>>>>>>>>>>>  			if (locked) {
>>>>>>>>>>>  				up_write(&fi->i_gc_rwsem[WRITE]);
>>>>>>>>>>>  				up_write(&fi->i_gc_rwsem[READ]);
>>>>>>>>>>> @@ -1030,6 +1055,8 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>>>>>>  
>>>>>>>>>>>  	if (++phase < 5)
>>>>>>>>>>>  		goto next_step;
>>>>>>>>>>> +
>>>>>>>>>>> +	return submitted;
>>>>>>>>>>>  }
>>>>>>>>>>>  
>>>>>>>>>>>  static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
>>>>>>>>>>> @@ -1057,6 +1084,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  	int seg_freed = 0;
>>>>>>>>>>>  	unsigned char type = IS_DATASEG(get_seg_entry(sbi, segno)->type) ?
>>>>>>>>>>>  						SUM_TYPE_DATA : SUM_TYPE_NODE;
>>>>>>>>>>> +	int submitted = 0;
>>>>>>>>>>>  
>>>>>>>>>>>  	/* readahead multi ssa blocks those have contiguous address */
>>>>>>>>>>>  	if (sbi->segs_per_sec > 1)
>>>>>>>>>>> @@ -1100,10 +1128,11 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  		 *                                  - lock_page(sum_page)
>>>>>>>>>>>  		 */
>>>>>>>>>>>  		if (type == SUM_TYPE_NODE)
>>>>>>>>>>> -			gc_node_segment(sbi, sum->entries, segno, gc_type);
>>>>>>>>>>> -		else
>>>>>>>>>>> -			gc_data_segment(sbi, sum->entries, gc_list, segno,
>>>>>>>>>>> +			submitted += gc_node_segment(sbi, sum->entries, segno,
>>>>>>>>>>>  								gc_type);
>>>>>>>>>>> +		else
>>>>>>>>>>> +			submitted += gc_data_segment(sbi, sum->entries, gc_list,
>>>>>>>>>>> +							segno, gc_type);
>>>>>>>>>>>  
>>>>>>>>>>>  		stat_inc_seg_count(sbi, type, gc_type);
>>>>>>>>>>>  
>>>>>>>>>>> @@ -1114,7 +1143,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>>>>>>>  		f2fs_put_page(sum_page, 0);
>>>>>>>>>>>  	}
>>>>>>>>>>>  
>>>>>>>>>>> -	if (gc_type == FG_GC)
>>>>>>>>>>> +	if (submitted)
>>>>>>>>>>>  		f2fs_submit_merged_write(sbi,
>>>>>>>>>>>  				(type == SUM_TYPE_NODE) ? NODE : DATA);
>>>>>>>>>>>  
>>>>>>>>>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>>>>>>>>>> index fa2381c0bc47..214dd6326b4b 100644
>>>>>>>>>>> --- a/fs/f2fs/node.c
>>>>>>>>>>> +++ b/fs/f2fs/node.c
>>>>>>>>>>> @@ -1584,8 +1584,10 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>>>>>>>>>>>  	return AOP_WRITEPAGE_ACTIVATE;
>>>>>>>>>>>  }
>>>>>>>>>>>  
>>>>>>>>>>> -void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>>>> +int f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>>>>  {
>>>>>>>>>>> +	int err = 0;
>>>>>>>>>>> +
>>>>>>>>>>>  	if (gc_type == FG_GC) {
>>>>>>>>>>>  		struct writeback_control wbc = {
>>>>>>>>>>>  			.sync_mode = WB_SYNC_ALL,
>>>>>>>>>>> @@ -1597,12 +1599,16 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>>>>  		f2fs_wait_on_page_writeback(node_page, NODE, true);
>>>>>>>>>>>  
>>>>>>>>>>>  		f2fs_bug_on(F2FS_P_SB(node_page), PageWriteback(node_page));
>>>>>>>>>>> -		if (!clear_page_dirty_for_io(node_page))
>>>>>>>>>>> +		if (!clear_page_dirty_for_io(node_page)) {
>>>>>>>>>>> +			err = -EAGAIN;
>>>>>>>>>>>  			goto out_page;
>>>>>>>>>>> +		}
>>>>>>>>>>>  
>>>>>>>>>>>  		if (__write_node_page(node_page, false, NULL,
>>>>>>>>>>> -					&wbc, false, FS_GC_NODE_IO, NULL))
>>>>>>>>>>> +					&wbc, false, FS_GC_NODE_IO, NULL)) {
>>>>>>>>>>> +			err = -EAGAIN;
>>>>>>>>>>>  			unlock_page(node_page);
>>>>>>>>>>> +		}
>>>>>>>>>>>  		goto release_page;
>>>>>>>>>>>  	} else {
>>>>>>>>>>>  		/* set page dirty and write it */
>>>>>>>>>>> @@ -1613,6 +1619,7 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>>>>>>>  	unlock_page(node_page);
>>>>>>>>>>>  release_page:
>>>>>>>>>>>  	f2fs_put_page(node_page, 0);
>>>>>>>>>>> +	return err;
>>>>>>>>>>>  }
>>>>>>>>>>>  
>>>>>>>>>>>  static int f2fs_write_node_page(struct page *page,
>>>>>>>>>>> -- 
>>>>>>>>>>> 2.18.0
>>>>>>>>>>
>>>>>>>>>> .
>>>>>>>>>>
>>>>>>>>
>>>>>>>> .
>>>>>>>>
>>>>>>
>>>>>> .
>>>>>>
>>>>>
>>>
>>> .
>>>
> 
> .
>